Protective device for a mass flow sensor disposed in an air intake channel

ABSTRACT

Known devices for measuring the mass of a flowing medium can be impaired in their measurement precision by fluid components carried along in the medium. The device according to the invention has a ricochet body, which is disposed upstream of the measuring element and is at least partially encompassed by an outer ring, where the outer ring constitutes a section inside the outer ring that tapers in the flow direction in order to deflect fluid components, which are carried along in the flow, away from the measuring element by means of the ricochet body. The device is useful for measuring the mass of a flowing medium, in particular for measuring the intake air mass of internal combustion engines.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 U.S.C. 371 application of PCT/DE 01/01279 filedon Mar. 31, 2001.

FIELD OF THE INVENTION

The invention is directed to an improved device for determining at leastone parameter of a flowing medium and more particularly to such a devicefor measuring a parameter of the intake air of an internal combustionengine.

DESCRIPTION OF THE PRIOR ART

A device is already known (DE-OS 35 15 206), in which a capturingelement is provided in the vicinity of a measuring element in ameasurement conduit of the device, in order to prevent dirt particles inthe air flow from adhering to the measuring element. The specifiedaccommodation of the capturing element in the vicinity of the measuringelement produces a leeward area downstream of the capturing element,which is intended to prevent dirt particles from adhering to themeasuring element. However, when there are fluid components carriedalong with the air flow, a condensation on the measuring element canoccur, which leads to a disadvantageous change in the characteristiccurve of the device and in its measuring precision.

EP 0 967 466 A1 has disclosed a device in which a damming body is usedto generate eddies. However, this leads to increased measurement signalnoise in the measuring element.

DE 196 32 198 A1 has disclosed a device in which a ricochet device isaccommodated upstream of the device, in a section of the flow line thattapers in the flow direction of the medium.

In this instance, the form of the line must be especially adapted inorder to form the tapering section. Due to the deviation from thestandard geometry, this leads to increased costs.

SUMMARY OF THE INVENTION

The device according to the invention for determining at least oneparameter of a flowing medium has the advantage over the prior art thatin particular fluid components of the air flow are prevented fromadhering to the measuring element so that a constantly precisemeasurement result can be achieved.

It has turned out that in particular, a prismatic embodiment of aricochet body advantageously achieves a particularly effective diversionof fluid components carried along in the air stream.

If the outer ring extends from the ricochet body to the measurementhousing, the measuring element can be advantageously protected fromcontaminants coming from the line.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is shown in a simplifiedfashion in the drawings and will be explained in detail herein below,with reference to the drawings, in which:

FIG. 1 shows a cross section through a device with a ricochet body andan outer ring,

FIG. 2 shows a longitudinal section along a line II—II in FIG. 1,through the intake line with the device.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a cross section through a device labeled 1, which is usedto determine at least one parameter of a flowing medium, in particularthe intake air of internal combustion engines. The engine can be amixture-compressing engine with externally supplied ignition or can alsobe an air-compressing, auto-ignition engine. As shown in detail in FIG.2, which is a longitudinal section along a line II—II in FIG. 1, ameasuring body 17 preferably has a slim, bar-shaped, block form, whichextends longitudinally in the direction of an insertion axis 10, and isinserted, e.g. in a sliding fashion, into an opening 6 of an intake line7 that constitutes a flow line, which opening is let into a wall 5. Forexample, the wall 5, which is indicated by cross-hatching, is part ofthe for example cylindrically embodied intake line 7, through which amedium flows, in particular the air aspirated by the internal combustionengine. The wall 5 of the intake line 7 defines a flow cross section,which in the case of the cylindrical intake line 7, for example, has acircular cross section, in the center of which a central axis 11 extendsin the direction of the flowing medium parallel to the wall 5 and isoriented perpendicular to the insertion axis 10. The direction of theflowing medium is indicated in FIGS. 1 and 2 by means of correspondingarrows 18 and runs from left to right there.

The measuring body 17 protrudes into the flowing medium and has ameasuring conduit 20, which accommodates at least one measuring element21 for determining at least one parameter of a medium flowing in theintake line 7. In this exemplary embodiment, a measuring element isused, which determines, for example, the volume flow of the flowingmedium. Other parameters that can be measured include, for example,pressure, temperature, a concentration of a medium component, or a flowspeed and are detected by means of suitable sensors.

The design of the measuring body 17 for determining a parameter of aflowing medium is sufficiently known to the expert, e.g. from DE-OS 4407 209, whose disclosure is incorporated into the current patentapplication by reference. The measuring body 17, however, is not limitedto this exemplary embodiment.

Upstream of the measuring element 21, a ricochet body 25 is accommodatedin the intake line 7, whose form is embodied so that components carriedalong in the flow 18 of the medium, in particular those in a fluid form,are deflected from the middle of the intake line 7, which region isindicated by the central axis 11, essentially to a lower part of thewall 5, which region is labeled with the reference numeral 8 and isshown at the bottom in FIG. 2.

As shown in detail in FIG. 1, the vertically disposed ricochet body 25has, for example, a prismatic form for this purpose, with an essentiallytriangular cross sectional area and a tip directed counter to the flow18. The ricochet body 25 can also be aerodynamically shaped.

For example, an outer ring 30 is disposed extending from the downstreamend 45 of the ricochet body 25 until or to an upstream beginning 46 ofthe measuring body 17. The outer ring 30 can be connected by means ofstruts (not shown) to the line 7 and/or to the ricochet body 25 and/orto the measuring body 17. In the flow direction 18 inside the outer ring30, this outer ring 30 constitutes a tapering section 31 in which anincrease in the flow speed of the medium or an acceleration occurs.

The outer ring 30 is disposed, for example, so that it partiallyencompasses, at a distance, an end surface 26 of the ricochet body 25oriented toward the flow direction 18 and then, for example, becomeswider at first in the inner diameter, viewed in the flow direction 18,so that the flow, which is deflected outward by the ricochet body 25,does not strike an inner wall 34 of the outer ring 30 frontally or at anacute angle. Then the inner wall 34 of the outer ring 30 tapers, causingthe gas to accelerate. The medium can flow through a first gap 38between the ricochet body 25 and the outer ring 30 and through a secondgap 39 between the measuring housing 17 and outer ring.

The circulation around the ricochet body 25 always causes flowseparations and eddies 32 in the vicinity downstream of the downstreamend 45 of the ricochet body 25. The eddies 32 are reduced in intensityby the section of the outer ring 30 that tapers in the main flowdirection and by the attendant acceleration of the gas so that noincreased measurement signal noise occurs in the measuring element 21.

Due to the fact that their inertia is considerably higher than that ofthe gas, fluid or solid particles in the line 7 that are entrained bythe gas strike against the ricochet body and are deflected by itradially outward in the direction of the wall 5. Only seldom can solidparticles get into the gap 38 and therefore into the tapering section31, which is constituted by the outer ring 30, since the outer ring 30extends from the ricochet body 25 to the measuring housing 17.

Those solid particles that do penetrate into this region, though, aredeflected past the measuring conduit 20 by being reflected against theinner wall 34 of the outer ring 30.

Due to its much greater dynamic viscosity, fluid that strikes againstthe ricochet body 25 then forms a wall film on the ricochet body; thiswall film is distributed on the inside 34 and outside 35 of the outerring 30 and therefore does not travel into the conduit 20.

The outer ring 30 is embodied as streamlined and, for example, isS-shaped.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the claims, thelatter being defined by the appended claims.

I claim:
 1. A device for determining at least one parameter of a mediumflowing in a line, which medium is in the form of a gas/fluid mixture,in particular the intake air of internal combustion engines, comprisinga measurement housing (17) provided in the line, at least one measuringelement (21) disposed in the measurement housing and around themeasurement housing and measuring element the flowing medium circulates,the measuring element being operable to determine parameters of themedium flowing in the line, a ricochet body (25) disposed upstream ofthe measuring element, an outer ring (30) disposed at least partiallybetween the ricochet body (25) and the measurement housing (17), and atapering section (31) inside the outer ring (30) constituted by theouter ring (30).
 2. The device according to claim 1, wherein thericochet body (25) is prismatic in form.
 3. The device according toclaim 1, wherein the ricochet body (25) is aerodynamically formed. 4.The device according to claim 1, wherein the outer ring (30) isaerodynamically formed.
 5. The device according to claim 4, wherein theouter ring (30) at least partially encompasses the ricochet body (25),at a distance (38).
 6. The device according to claim 4, wherein theouter ring (30) at least partially encloses the measurement housing(17), at a distance.
 7. The device according to claim 1, wherein theouter ring (30) is embodied as S-shaped.
 8. The device according toclaim 7, wherein the outer ring (30) at least partially encompasses thericochet body (25), at a distance (38).
 9. The device according to claim7, wherein the outer ring (30) at least partially encloses themeasurement housing (17), at a distance.
 10. The device according toclaim 1, wherein the outer ring (30) at least partially encompasses thericochet body (25), at a distance (38).
 11. The device according toclaim 10, wherein the outer ring (30) at least partially encloses themeasurement housing (17), at a distance.
 12. The device according toclaim 1, wherein the outer ring (30) at least partially encloses themeasurement housing (17), at a distance.